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displayed_sidebar: "English"
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# hll_raw_agg

## Description

This function is an aggregate function that is used to aggregate HLL fields. It returns an HLL value.

## Syntax

```Haskell
hll_raw_agg(hll)
```

## Parameters

`hll`: the HLL column that is generated by other columns or based on the loaded data.

## Return value

Returns a value of the HLL type.

## Examples

```Plain
mysql> select k1, hll_cardinality(hll_raw_agg(v1)) from tbl group by k1;
+------+----------------------------------+
| k1   | hll_cardinality(hll_raw_agg(`v1`)) |
+------+----------------------------------+
|    2 |                                4 |
|    1 |                                3 |
+------+----------------------------------+
```
